The present Continuation-In-Part application relates to the process of separation of Mo-99 produced by the apparatuses and methods of the parent and grand-parent applications. The present invention generally relates to neutron generators, and more particularly to a neutron generator employing an electron accelerator for producing thermal neutrons. More specifically, this invention relates to a method of enhancing the thermal neutron flux for the production of medical and industrial isotopes including Molybdenum-99 and other isotopes. Yet more specifically, this invention relates to a method of very large enhancements of thermal neutron fluxes due to the use a homogeneous mixture of D2O and H2O with
The efficient production of certain short-lived isotopes, including Molybdenum-99, requires a high flux of thermal neutrons. Reactors producing such isotopes experience outages which disrupt the availability of needed neutron sources. Alternatives to nuclear reactors, as a neutron source, include cyclotrons and electron accelerators. However, such systems capable of production of a high thermal flux have posed such expense and size so as to render them impractical for use in a clinical setting.
Known electron accelerators, capable of producing high energy neutrons, are large and impose high operating expenses. Additionally, neutrons of such energy require massive shielding and are not effectively thermalized. The patents and publications referred to herein are provided herewith in an Information Disclosure Statement in accordance with 37 CFR 1.97.
Processes of the production of Mo-99 are known via aqueous solution nuclear reactors. The production of Mo-99 is addressed in Homogeneous Aqueous Solution Nuclear Reactors for the Production of Mo-99 and other Short Lived Radioisotopes, IAEA-TECDOC-1601, September 2008. Page 17 addresses the Optimization of 200 kW Medical Isotope Production Reactor Design; SONG, NUI; Nuclear Power Institute of China, Sichuan Nuclear Society, China; p17 IAEA-Tecdoc-1601:9/08 where Mo-99 is produced via a homogeneous aqueous reactor with an operational cycle followed by shutdown and transfer, via a fuel transfer system, of the fuel solution to a storage pot, separate from the reactor vessel, where isotopes are adsorbed from the fuel solution.
IAEA-TECDOC-515; FISSION MOLYBDENUM
FOR MEDICAL USE—target not solution reactor. HEU targets. Alkaline dissolution of different U-Al targets. These processes differ mainly in the subsequent purification steps of the crude 99Mo. K. A. Burrill (Canada), R. Münze (GDR) and H. Kudo (Japan) described 99Mo production processes that use acidic (HNO3) dissolution.
ANL/CMT/CP 102990: PRODUCTION OF MO-99 FROM LEU TARGETS ACID-SIDE PROCESSING—targets foil, pins, rods not solution reactor. Cintichem process, foils dissolved. The separation process consists of dissolving the irradiated LEU foil in a reusable dissolver, precipitating the molybdenum with cx-benzoin oxime (ABO), washing the precipitate, dissolving the precipitate, then passing the resultant solution through two purification columns.
ANL/CMT/CP 102989 PRODUCTION OF MO-99 FROM LEU TARGETS BASE-SIDE PROCESSING; HEU to LEU foil with digestion by sodium hydroxide.
T. N. van der Walt1, and P. P. Coetzee; The isolation of 99Mo from fission material for use in the 99Mo/99 mTc generator for medical use; Radiochim. Acta 92, 251-257 (2004); Target dissolved in sodium hydroxide. The radionuclides of molybdenum and iodine were separated by anion exchange chromatography, in alkaline medium, from the bulk aluminum and radionuclides of other elements, such as barium, strontium and tellurium. 99Mo was selectively eluted with a slightly alkaline lithium sulphate solution, leaving the iodine radionuclides on the resin. The 99Mo eluant was acidified with oxalic acid and nitric acid and 99Mo separated from the remaining aluminum and other radionuclides by anion exchange chromatography, in acid medium.
Initial Generation and Separation of 99Mo at Sandia National Laboratories; Methods and Applications of Radioanalytical Chemistry IV Conference; Kailua-Kona, Hi., Apr. 6-12, 1997; Medical Radioisotopes Production; Apr. 11, 1997. Target not solution. Cintichem process consists of four primary stages: 1) irradiation of a UO2-coated isotope production target, 2) the irradiated UO2 coating is dissolved from the inner surface of the target, 3) the Mo in the dissolved coating solution is precipitated, filtered out and redissolved, and 4) the Mo solution is purified of dissolution by-products and contaminants.
ORNL/TM-2009/181; An Account of Oak Ridge National Laboratory's Thirteen Nuclear Reactors; August 2009. P12 AQUEOUS HOMOGENEOUS REACTOR. 93% enriched uranium as uranyl sulfate dissolved in water. Power reactor. P18-A key attraction for the liquid fuel reactor is ease of reprocessing the fuel to remove fission products with no isotopes or processing steps indicated. The volatile products from the HRT were removed by the gas separator in the core exit line. After passage through the steps shown in
The present invention is directed to a method of very large enhancements of thermal neutron fluxes resulting from the irradiation of a vessel (200) containing a homogeneous mixture of a solution of D2O and H2O, comprising a primary target (400) mixed with Low Enriched Uranium (LEU), comprising a secondary target (500), where the vessel (200) is enclosed with Nickel and or Polyethylene neutron reflector (600) material. In the preferred embodiment the source of irradiation is from an electron accelerator, indicated here as LINAC (100). An electron beam (120) irradiates a gamma converter (300) which is affixed to the vessel (200) for converting the electron beam (120) into photons for producing high energy neutrons in a photonuclear reaction between the photons and the photoneutron target, and for moderating the high energy neutrons to generate the thermal neutrons. The electron beam (120) has an energy level that is sufficiently low as to enable the material to moderate the high energy neutrons resulting from the photonuclear reaction. The receiving device is enclosed, with the exception of the path required for the electron beam (120) to irradiate the converter (300), in a material which reflects neutrons back into the photoneutron target thereby realizing an enhancement of the neutron flux to which the photoneutron target is exposed. In a preferred embodiment, a secondary target (500) of LEU is placed within the receiving device with a primary target (400), which, when radiated by the enhanced neutron flux, fissions thereby further and greatly enhancing the neutron flux. The use of LEU, as a secondary target (500), results in the production of useful isotopes including Molybdenum-99.
The CIP Mo-99 Process regards the extraction and collection of Mo-99 produced by the apparatus and method of the foregoing paragraph [0004]. The vessel (200) solution produced by the irradiation of the primary target (400) is homogeneously mixed with the secondary target (500) produces isotopes including Mo-99. The irradiated solution, comprising the reaction vessel solution (800), is pumped from the vessel (200) by access to the vessel (200) chamber which is adapted, by a deliver tube system (210) which is referred to in paragraph [0014], for periodically introducing and extracting the reaction vessel solution (800) from the vessel (200). The reaction vessel solution (800) is pumped continuously through a heat exchanger (900) is filtered (1000), pumped through an absorbent (1100) and then returned to the vessel (200). As the reaction vessel solution (800) is pumped Mo-99 is loaded into at least one column (1120) and is acid washed (1200). The at least one column (1120) is then neutralized. The Mo-99 is then removed from the at least one column (1120), is washed, pumped through a resin column (1600) loading Mo-99 on the resin column (1600). The resin column (1600) is washed and neutralized. Then Mo-99 is removed from the resin column (1600) and collected in a precipitation vessel (1700). The Mo precipitate is filtered, washed, heated and transferred to a dissolution vessel (2000). The Mo is redissolve producing a Mo solution which is filtered and collected.
The foregoing and other features and advantages of the present invention will become more readily appreciated as the same become better understood by reference to the following detailed description of the preferred embodiment of the invention when taken in conjunction with the accompanying drawings, wherein:
The preferred embodiment of this disclosure is a “hybrid” system of an accelerator-subcritical reactor with a primary target (400) comprised of a solution of D2O and H2O with sufficient LEU, as a secondary target (500), homogeneously mixed with the primary target (400). The primary target (400) and secondary target (500) are contained in a vessel (200), formed for example from metals resistant to corrosion including Al, Stainless Steel or Zircaloy, which, in the preferred embodiment, is encased in reflectors of Polyethylene and or Nickel. In an alternative embodiment the vessel (200) may be spherical having a cooling system (700) at the exterior of the vessel (200). When the homogeneously mixed primary target (400) and secondary target (500) are irradiated there is a resulting very large enhancement in thermal flux and hence the production of Molybdenum-99. The disclosure herein, of a method of producing very large enhancements in thermal flux is realized by attention to the mass of U-235, the thicknesses of the reflector of Nickel and or Polyethylene and vessel geometry. This invention discloses combinations which produce a “resonance” effect and hence a very large enhancement in neutron thermal flux.
The presence of U-235 employed in the secondary target (500) plays a very important role. The disclosed mass of U-235 results in dramatically increased production of Molybdenum-99 because of the “high energy” neutrons created in the fission spectrum of 1 MeV-20 MeV. The primary target of D2O and H2O plays two very important roles. First, D2 provides the target for the required photoneutron effect. The primary target (400) of the D2O and H2O solution thermalizes photoneutrons and more importantly fission neutrons from U235 and U238.
In
The gamma converter (300) is made of a material having an atomic number or Z of at least 26, but preferably higher than 70, for example, tantalum (Ta, Z=73) or tungsten (W, Z=74) or depleted uranium (U, Z=92). When the electron beam (120) is incident on the front surface of the converter (300), bremsstrahlung photons are produced as the electrons slow down in the converter. This process is most efficient in producing photons when the electrons are stopped in a material of high atomic number, such as Ta or W, for example, used in the preferred embodiment.
In an alternative embodiment, seen in
The reflector (600) can be of any neutron reflecting material such as, for example, graphite, Polyethylene, Nickel or steel. In the preferred embodiment, the reflector (600), when Polyethylene, has a thickness of approximately 1.5 cm to 6.0 cm and when Nickel has a thickness of 1.0 cm to 4.0 cm. The thickness of the reflector (600) may vary depending on the size of the photoneutron primary target (400) of D2O and H2O contained within the vessel (200). A different reflector (600) material may be used on the top or bottom of the vessel (200) than on the radial side of the vessel. A sample of the primary target (400) or of the mixture of the primary target (400) and the secondary target (500) can be introduced and withdrawn, as known to those of ordinary skills in radiation arts, via a delivery tube from the vessel (200).
In the alternative embodiment the reflector (600) Polyethylene covers the vessel (200) exterior and cooling system (700), is of a thickness range of 1 to 10 cm with an optimum thickness of 2 to 4 cm. In this alternative embodiment neutron reflector (650) material of Nickel is affixed distal to the reflector (600) material and vessel (200) and may be affixed at the interior of the hot cell. The Polyethylene reflector (600) at the exterior of the vessel (200) and covering the cooling system (700) may be applied via spray. It is recognized that Polyethylene is both a neutron reflector and a moderator.
In operation, the secondary target (500) to be irradiated with thermal neutrons is introduced into the neutron generating vessel (200). The LINAC (100) is set by a control device to generate an electron beam (120) having the desired energy level, which is converted into photons by the gamma ray converter (300). The photons are injected into the vessel (200), where neutrons are produced through a photonuclear reaction with the primary target (400) comprised of a solution of heavy water and light water. In the present invention, neutrons are produced in a photonuclear reaction in deuterium D2. Deuterium has a low photonuclear threshold energy of 2.23 MeV. Thus, photons created from the LINAC (100) having electron energies in the range of approximately 5 MeV-15 MeV are sufficient to cause a photonuclear reaction in heavy water and generate high energy neutrons. The high energy neutrons are then slowed down, or moderated, to thermal energies by heavy water. Because of its small neutron absorption cross section and low effective atomic mass, heavy water functions also as a moderator. The thermal neutrons are then captured by the sample, here the secondary target (500) comprised preferably of LEU, which is converted to Molybdenum-99 and other isotopes.
This invention is the method of creating large and very large enhancements of thermal neutron fluxes. The method for creating large enhancements is by the use of an electron accelerator LINAC (100) irradiating, with an electron beam (120), a gamma ray converter (300) with the resulting gamma ray radiation of a primary target (400) of D2O and H2O contained within a vessel (200) which is enclosed within a neutron reflector (600) of either Polyethylene or Nickel. Further, the creation of very large enhancements is of the neutron flux is by the incorporation of a secondary target (500) of LEU into the D2O/H2O solution.
From the foregoing description, it should be understood that a thermal neutron generator capable of greatly enhanced neutron flux by the use of reflectors (48) when the primary target (400) is a solution of D2O and H2O and, further, capable of a very great enhancement of neutron flux, within the primary target (400), when a secondary target (500) of enriched Uranium is homogeneously mixed with the primary target (400). The effect of creating a very great enhancement of neutron flux when a secondary target (500) is present is to increase the efficiency of production of useful isotopes including Molybdenum-99. Here, for vessel (200) sizes expected the secondary target (500) will be within a range of LEU from 18 kg to 25 kg. The secondary target (500) of LEU is a solution with U-235 ions in solution. 20 kg of Uranium, at 19% LEU, contains 3.8 kg U-235. In the preferred embodiment the primary target (400) of a solution of D2O and H2O combined with a secondary target (500) of LEU will have LEU enriched in the range of 15% to 19% U-235.
In the alternative embodiment the primary target (400) is a solution of D2O and H2O in the range of 80% to 100% D20 and 0% to 20% H2O and is preferred to be maintained at 90% D20. In this alternative embodiment the primary target (400) of a solution of D2O and H2O combined with a secondary target (500) of LEU will have LEU enriched in the range of 11% to 19% U-235 with preferred LEU enrichment at 15% U-235. The total Uranium concentration will be less than or equal to 50 grams/liter with the total Uranium content with a range of 10 to 20 Kg.
Results of MCNPX Code calculations showing the effect of Nickel and Polyethylene reflection are seen in
When a secondary target (500) of Uranium is homogeneously mixed with the primary target (400) of D2O and H2O, the use of a reflector (600) of Nickel shows a very large enhancement in
In the alternative embodiment the vessel (200) will be water cooled. In the alternative embodiment the converter (300) will have a thickness in the range of 0.1 to 0.6 cm and is preferred at 0.35 cm.
The present CIP Process, noted in the flow chart of
The reaction vessel solution (800) is pumped continuously through a heat exchanger (900) and filter (1000), to remove insoluble fission products and corrosion products, then continuously through an absorbent (1100) and then returned to the vessel (200).
In the preferred embodiment reaction vessel solution (800) is pumped continuously at 30 ml/min for 7 days through the heat exchanger (900) to reduce the reaction vessel solution (800) temperature to no more than 30° C. The absorbent (1100), in the preferred embodiment, is provided by column chromatography by at least one 60 ml Al203 column (1120) with resultant loading of Mo-99 on the column (1120). Those of ordinary skills in the chemical arts will recognize that other absorbents (1100) are known and may be used. In the preferred embodiment the solution is returned to the vessel (200) continuously at 30 ml/min for 7 days.
The loaded at least one column (1120) is then acid washed (1200). In the preferred embodiment the acid wash is with 5 column volumes of 0.1 M HN03 with the acid collected in a waste acid storage tank (1300). The at least one column (1120) is then neutralized. In the preferred embodiment the at least one column (1120) is neutralized with 5 column (1120) with the water collected in the waste acid storage tank (1300). Following the acid washed (1200) at least one column (1120) is then washed with 0.01 M NH4OH to alkify the column (1120). In the preferred embodiment this wash is with 5 column volumes of 0.01 M NH4OH with this wash collected in a waste base storage tank (1400).
The Mo-99 is then removed from the at least one column (1120) by washing with 1 M NH4OH with this wash of 1 M NH4OH and Mo-99 collected in an adjustment vessel (1500). In the preferred embodiment the wash is with 5 column (1120) volumes of 1 M NH4OH. Added to the adjustment vessel (1500) containing the wash of NH4OH and Mo-99 is 5 M NaOH to make collected Mo-99 1M NaOH. This solution is then pumped through an anion-exchange resin column (1600) thereby loading Mo-99 on the resin column (1600). In the preferred embodiment the resin column (1600) is at least one AG MP-1 column. The 1M NaOH solution is collected in the waste base storage tank (1400).
The at least one resin column (1600) is then washed with 1 M MNaOH. In the preferred embodiment the wash of the resin column (1600) is with 5 resin column volumes of 1M NaOH. This wash is collected in the waste base storage tank (1400). Next the at least one resin column (1600) is neutralized. In the preferred embodiment this neutralization is with 5 resin column (1600) volumes of water. This water is collected in the waste base storage tank (1600). Then Mo-99 is removed from the resin column (1600) by the addition of 2M HNO3 to the resin column (1600). The Mo-99 is then collected in a precipitation vessel (1700). Next, added to the precipitation vessel (1700) is 2 wt % alph-benzoinoxime in 0.4 M NaOH in 20:1 weight ratio to Mo, thereby precipitating Mo followed by filtering of the Mo precipitate via a precipitate filter (1800). The filtrate is collected in the waste acid storage tank (1300).
The Mo precipitate is washed with a precipitate acid wash (1900). In the preferred embodiment the precipitate acid wash (1900) is dilute sulfuric acid. The precipitate acid wash (1900) is collected in the waste acid storage tank (1300). The Mo precipitate is heated to drive off liquids and organics and then transferred to a dissolution vessel (2000). Added to the Mo precipitate is 0.2 M NaOH with NaOCl to redissolve the Mo producing a Mo solution which is filtered with a particulate filter (2100). In the preferred embodiment the particulate filter (2100) is a 0.2 micron filter. Next the filtered Mo is collected.
The Mo-99 Extraction and Collection Process Steps are summarized as follows:
NHNO3P-1: Pump reaction vessel solution continuously at 30 ml/min for 7 days through heat exchanger (reduce temperature to no more than 30° e) and filter to remove insoluble fission products and corrosion products.
P-2: Pass reaction vessel solution continuously through Al2O3 column loading Mo-99 on the column.
P-3: Return reaction vessel solution to reaction vessel continuously at 30 ml/min for 7 days.
P-4: Add 5 column volumes of 0.1 M HNO3 to wash Al2O3 column.
P-5: Collect 5 column volumes of 0.1 M HNO3 in waste acid storage tank.
P-6: Add 5 column volumes of water to neutralize Al2O3 column.
P-7: Collect 5 column volumes of water in waste acid storage tank.
P-8: Add 5 column volumes of 0.01M NH4OH to alkify Al2O3 column.
P-9: Collect 5 column volumes of 0.01M NH4OH in waste base storage tank.
P-10: Add 5 column volumes of 1M NH4OH to remove Mo-99 from Ah03 column.
P-11: Collect 5 column volumes of 1M NH4OH with Mo-99 in adjustment vessel.
P-12: Add 5 M NaOH to make collected Mo-99 1M NaOH.
P-13: Pump Mo-99 solution through AG MP-1 column, loading Mo-99 on column.
P-14: Collect 1 M NaOH solution in waste base storage tank.
P-15: Add 5 column volumes of 1M NaOH to wash AG MP-1 column.
P-16: Collect 5 column volumes of 1M NaOH in waste base storage tank.
P-17: Add 5 column volumes of water to neutralize AG MP-1 column.
P-18: Collect 5 column volumes of water in waste base storage tank.
P-19: Add 5 column volumes of 2 M HNO3 to remove Mo-99 from AG MP-1 column.
P-20: Collect Mo-99 in precipitation vessel.
P-21: Add 2 wt % alph-benzoinoxime in 0.4 M NaOH in 20:1 weight ratio to Mo, precipitating Mo.
P-22: Filter Mo precipitate.
P-23: Collect filtrate in waste acid storage tank.
P-24: Wash Mo precipitate with dilute sulfuric acid.
P-25: Collect dilute sulfuric acid in waste acid storage tank.
P-26: Heat precipitate to drive off liquids and organics.
P-27: Transfer precipitate to dissolution vessel.
P-28: Add 0.2 M NaOH with NaOCl to redissolve Mo.
P-29: Filter Mo solution with 0.2 micron filter to remove particulate.
P-30: Collect filtered Mo product.
The Mo-99 Process Description is as follows:
While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. Various features of the invention are set forth in the appended claims.
This application, titled “Advanced Once-Through Processing for Extracting Molybdenum-99 from Deuterium and Low Enriched Uranium Solutions”, is a Continuation in Part pending from the parent application titled “Very Large Enhancements of Thermal Neutron Fluxes Resulting in a Very Large Enhancement of the Production of Molybdenum-99 Including Spherical Vessels”, USPTO application Ser. No. 12/649,915, filed Dec. 30, 2009 which is a CIP from the grand-parent application which was titled “Very Large Enhancements of Thermal Neutron Fluxes Resulting in a Very Large Enhancement of the Production of Molybdenum-99”, application Ser. No. 12/543,408 filed Aug. 18, 2009. Filed herewith is the original Declaration of the inventor, Dr. Fu-Min Su and the Power of Attorney. Additions by this Continuation In Part Application are added in BOLDED LETTERS. The application is otherwise identical to Continuation-In-Part application Ser. No. 12/649,915. New Claims are added in Bold. Claims 1 through 22 in the parent and grandparent applications will be subject to examination relative to the Parent and Grand-Parent application. Herein are filed 2 independent and 3 dependent claims relating to this CIP. All Drawings for the Parent and Grandparent applications are filed with this Continuation in Part Application. FIG. 9 is a flow chart illustrating the process of this CIP.